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# Thread: 0.004" micro drill bit - photo

1. ## The Following 3 Users Say Thank You to Altair For This Useful Post:

baja (Jan 8, 2020), Seedtick (Jan 7, 2020), Tonyg (Jan 10, 2020)

2. Okay, I'll bite,

When might somebody need to drill such a tiny hole and how many drills are you likely to break when you try to do it will it drill a hole in ferous metal or paper or aluminium or something else ?

3. .004" if that's all the hole you need...you could just as well do without it.
Seedtick

4. Originally Posted by steamingbill
Okay, I'll bite,

When might somebody need to drill such a tiny hole and how many drills are you likely to break when you try to do it will it drill a hole in ferous metal or paper or aluminium or something else ?
to make holes in the spray nozzles for fuel injectors

5. Thank you for sharing Frank.

I think what is more impressive is the fact someone has been able to make a drill that size. It must be fluted to allow the swarf to escape so the outside diameter is 0.004" but the core will be even smaller let alone grinding the cutting clearance angle on the tip. This to me is a fantastic achievement in making the drill let alone using it. I calculated the spindle speed would be 76500rpm for mild steel. I use 0.2 mm cutters at work on a CNC engraver but only on plastic and depth of cut 0.02 mm per pass. So appreciate the difficulty in using this sized diameter drill

Formula used to calculate spindle speed:
Cutting speed of mild steel 24 m/min x 1000 / Pi (3.14) x diameter of drill (0.1 mm). Therefore 24000/0.314=76433 rpm

The spindle speed also leads to another engineering problem.

The Home Engineer

6. .004 Yikes.
I made 180 blow mold nozzles, drilled in 4 opposing rows, 44 total holes each. Those were .015 diameter, fastest spindle I could find, only 9000. Not 63,000.
So, I had the lightest touch imaginable for quite some time later.
Fixture used 01 drilled and heat treated for effective drill bushing in favored 10 diameters thickness [.150]. It was positioned one diameter from part, above centerline. The carrier had pin to register in fixture notched to regulate spacing of opposite sides. After 2 rows were done, moved pin to second position. That set other rows halfway between the first. It went remarkably fast; keeping fixture and bushing in place, moving the part instead. Targeting 11 bushings would have been a numbing endeavor.

7. Thankfully I never had to try and drill holes in sub mm size being around spindles spinning 2 to 5 x faster than a dentist drill on machines that weigh a few tons is not my idea of pleasant working conditions I'll take an old 13" to 20" column radial arm with a spindle range from 15 RPM to 1800 RPM any day over one of those things or my square post Cleereman or my 6 drill

8. Years ago I heard a story about the Russians sending their smallest drill bit to the US to show off their technology. The story goes that we evaluated it and drilled a hole through the side of it and sent it back to them. This was during the space race. I don't know if this is BS or factual, but I thought it was funny.

9. ## The Following User Says Thank You to owen moore For This Useful Post:

Toolmaker51 (Jan 11, 2020)

10. If it was before EDM, that would be remarkable.
Similar story is US-Japan. They send little drill, we return cross drilled.
They return it tapped...

11. Originally Posted by Toolmaker51
If it was before EDM, that would be remarkable.
Similar story is US-Japan. They send little drill, we return cross drilled.
They return it tapped...
I've heard that story but it was the Germans who tapped it

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